Field of the Invention
The present invention relates to a sheet feeding device that individually separates and feeds a sheet, and an image forming apparatus, such as a copying machine or a printer, provided with the sheet feeding device.
Description of the Related Art
Conventionally, in a sheet feeding device mounted on an image forming apparatus such as a printer, a facsimile machine, or a copying machine, as disclosed in Japanese Patent Laid-Open No. 2009-249089 and Japanese Patent Laid-Open No. 2001-199559, there is used a separating mechanism that individually separates a sheet stacked in a storage case or the like. As the separating mechanism, a retard separating mechanism using a feed roller and a retard roller that form a pickup roller and a separation portion, and a separating mechanism using a separating member (a separation roller or a friction pad) and a feed roller serving also as a pickup and a feeding function are often used.
A paper feeder of Japanese Patent Laid-Open No. 2009-249089 has a paper returning claw to perform a stable feeding operation. With this configuration, even when a sheet is staying near the separating mechanism, which may cause overlap feeding, an operation of the paper returning claw disposed on a sheet conveying path is appropriately controlled using a clutch or the like, so that a front end of the sheet is pushed back to an upstream side by the returning claw, and further to a sheet placing portion. This enables a continuous, stable feeding operation without overlap feeding.
In a sheet carrier of Japanese Patent Laid-Open No. 2001-199559, after separation by a separating mechanism, the side restricting plates are moved, and a press contact of the friction member with the separation roller, which form the separating mechanism, is canceled. Then, based on the positional information of the side end of the documents, which is detected by a document side end detecting sensor provided on the side restricting plates, the movement of the side restricting plates is stopped. With this configuration, it is possible to prevent skew feeding or jamming of a sheet, irrespective of a positional variation of the side restricting plates or the variation in a sheet size.
However, in these conventional sheet feeding devices, due to the following reasons, skew feeding or jamming has occurred during sheet conveyance, and cost has been increased.
That is, in the paper feeder of Japanese Patent Laid-Open No. 2009-249089, skew feeding during manual feeding is maintained by a side regulation plate provided on a stack tray and rigidity of the sheet. However, this depends on the rigidity, variations in a size width, and displacement of the stacking position of the stacked sheet, or an operation state of the side regulation plate by a user, inhibiting sufficient prevention of skew feeding. In some cases, feeding without regulation of the side regulation plate may cause skew feeding, jamming, wrinkles, scratches, or the like.
On the other hand, in the sheet carrier disclosed in Japanese Patent Laid-Open No. 2001-199559, although it is possible to prevent skew feeding of a sheet, a position detecting portion and a moving portion for the side restricting plates are required, increasing cost.
Accordingly, it is desirable to prevent damage, wrinkles, scratches, jamming of a sheet due to skew feeding or rotation (fan) of the sheet during feeding of the stacked sheet, and to suppress a cost increase.